build: skip xenapi driver when building for RHEL
build: skip xenapi driver when building for RHEL

https://bugzilla.redhat.com/show_bug.cgi?id=643118

* libvirt.spec.in: Provide xenapi conditionals.

jardasgit/libvirt,elmarco/libvirt,nertpinx/libvirt,leilihh/libvirt,novel/fbsd-libvirt,eskultety/libvirt,eskultety/libvirt,taget/libvirt,andreabolognani/libvirt,elmarco/libvirt,novel/fbsd-libvirt,sshah-solarflare/Libvirt-PCI-passthrough-,datto/libvirt,rbu/libvirt,agx/libvirt,olafhering/libvirt,sshah-solarflare/Libvirt-PCI-passthrough-,dumbbell/libvirt,trainstack/libvirt,jfehlig/libvirt,emaste/libvirt,nertpinx/libvirt,dumbbell/libvirt,rmarwaha/libvirt,rmarwaha/libvirt1,datto/libvirt,zippy2/libvirt,nertpinx/libvirt,wiedi/libvirt,foomango/libvirt,wiedi/libvirt,jeckersb/libvirt,jardasgit/libvirt,usc-isi/libvirt,kantai/libvirt-vfork,rmarwaha/libvirt,zhlcindy/libvirt-1.1.4-maintain,soulxu/libvirt-xuhj,agx/libvirt,iam-TJ/libvirt,agx/libvirt,jeckersb/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,jfehlig/libvirt,eskultety/libvirt,iam-TJ/libvirt,usc-isi/libvirt,dumbbell/libvirt,libvirt/libvirt,cbosdo/libvirt,rlaager/libvirt,jeckersb/libvirt,jeckersb/libvirt,sshah-solarflare/Libvirt-PCI-passthrough-,kantai/libvirt-vfork,elmarco/libvirt,foomango/libvirt,zippy2/libvirt,usc-isi/libvirt,rmarwaha/libvirt,trainstack/libvirt,warewolf/libvirt,sshah-solarflare/Libvirt-PCI-passthrough-,rbu/libvirt,novel/fbsd-libvirt,VenkatDatta/libvirt,dumbbell/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,danwent/libvirt-ovs,leilihh/libvirt,foomango/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,siboulet/libvirt-openvz,emaste/libvirt,rlaager/libvirt,elmarco/libvirt,libvirt/libvirt,jeckersb/libvirt,fabianfreyer/libvirt,rlaager/libvirt,danwent/libvirt-ovs,cbosdo/libvirt,warewolf/libvirt,cbosdo/libvirt,andreabolognani/libvirt,trainstack/libvirt,wiedi/libvirt,bjzhang/libvirt,fabianfreyer/libvirt,cbosdo/libvirt,wiedi/libvirt,fabianfreyer/libvirt,zippy2/libvirt,rlaager/libvirt,olafhering/libvirt,leilihh/libvirt,crobinso/libvirt,jfehlig/libvirt,warewolf/libvirt,soulxu/libvirt-xuhj,iam-TJ/libvirt,novel/fbsd-libvirt,danwent/libvirt-ovs,trainstack/libvirt,novel/fbsd-libvirt,siboulet/libvirt-openvz,VenkatDatta/libvirt,taget/libvirt,iam-TJ/libvirt,VenkatDatta/libvirt,foomango/libvirt,iam-TJ/libvirt,agx/libvirt,soulxu/libvirt-xuhj,rmarwaha/libvirt,datto/libvirt,nertpinx/libvirt,emaste/libvirt,datto/libvirt,soulxu/libvirt-xuhj,eskultety/libvirt,eskultety/libvirt,emaste/libvirt,rbu/libvirt,rlaager/libvirt,emaste/libvirt,warewolf/libvirt,kantai/libvirt-vfork,siboulet/libvirt-openvz,novel/fbsd-libvirt,crobinso/libvirt,wiedi/libvirt,rbu/libvirt,taget/libvirt,siboulet/libvirt-openvz,zhlcindy/libvirt-1.1.4-maintain,warewolf/libvirt,novel/fbsd-libvirt,foomango/libvirt,dumbbell/libvirt,dumbbell/libvirt,rbu/libvirt,zippy2/libvirt,rmarwaha/libvirt1,novel/fbsd-libvirt,jeckersb/libvirt,rmarwaha/libvirt1,jardasgit/libvirt,emaste/libvirt,zhlcindy/libvirt-1.1.4-maintain,libvirt/libvirt,nertpinx/libvirt,VenkatDatta/libvirt,leilihh/libvirt,rmarwaha/libvirt1,agx/libvirt,trainstack/libvirt,warewolf/libvirt,shugaoye/libvirt,rmarwaha/libvirt1,wiedi/libvirt,bjzhang/libvirt,danwent/libvirt-ovs,shugaoye/libvirt,leilihh/libvirt,danwent/libvirt-ovs,taget/libvirt,usc-isi/libvirt,iam-TJ/libvirt,emaste/libvirt,taget/libvirt,shugaoye/libvirt,iam-TJ/libvirt,kantai/libvirt-vfork,novel/fbsd-libvirt,rmarwaha/libvirt1,shugaoye/libvirt,rmarwaha/libvirt,usc-isi/libvirt,leilihh/libvirt,crobinso/libvirt,siboulet/libvirt-openvz,bjzhang/libvirt,jeckersb/libvirt,datto/libvirt,bjzhang/libvirt,trainstack/libvirt,zhlcindy/libvirt-1.1.4-maintain,jfehlig/libvirt,andreabolognani/libvirt,elmarco/libvirt,libvirt/libvirt,trainstack/libvirt,cbosdo/libvirt,bjzhang/libvirt,fabianfreyer/libvirt,kantai/libvirt-vfork,crobinso/libvirt,warewolf/libvirt,olafhering/libvirt,zhlcindy/libvirt-1.1.4-maintain,sshah-solarflare/Libvirt-PCI-passthrough-,shugaoye/libvirt,wiedi/libvirt,rmarwaha/libvirt,soulxu/libvirt-xuhj,olafhering/libvirt